Overall I am very satisfied with the cheap clock. Operation is intuitive and the display is a good size. A key must be pressed for 2 seconds before the start. This prevents an unwanted start when the clock or similar time in a pocket lies. Training zones can be set,% of maximum heart rate are also displayed. But I have found that now and then the heart rate monitor does not function properly and the short pulse displayed can vary greatly. Therefore -1 star
